1. Field of the Invention
The present invention relates to an corrosion resistant copper alloy tube which is used as a refrigerant copper alloy tube or a heat exchanger copper alloy tube and a fin-tube heat exchanger which is used for an air-conditioner, particularly relates to an corrosion resistant copper tube and a fin-tube heat exchanger having improved corrosion resistant property against an ant-nest type corrosion.
2. Description of Prior Art
A tube which was made of copper deoxidized by phosphorous has been widely used for the conventional refrigerant tube or the conventional heat exchanger tube generally due to its better bending and brazing properties.
In these tubes, however, organic materials such as lubricant oil or process oil and organic solvents unavoidably remaining on the surface of the fins and tubes after the tubing and fabrication processes may decompose during the repeated deposit and evaporation of water due to a coolant and during the exposure to peculiar temperature/moisture and air-exchange environment created as a nature of its construction to form carboxylic acids which cause peculiar corrosion showing local ant-nest type corrosion on the surface of the tube.
Thus, a large amount of lubricant oil has been used in the fabrication process of the heat exchanger, however considering recent environmental problems there is a trend to avoid the degreassing wash by organic solvents and rather to use volatile lubricant oil instead of such organic solvents. In this case, even though the base oil itself is volatile, such lubricant oil still contains some oil additives which may remain on the surface of the copper tube.
Therefore, there is an increasing risk for the ant-nest type corrosion in future according to more usage of volatile lubricant oil, compared to the case the degrase wash was performed using organic solvents. Reflecting such circumstance, measurements for the ant-nest type corrosion are attracting the attention of the industry as one of serious problems. Further, increase of remaining organic materials on the surface of the copper alloy tube is creating another problem of poor conjunction of tube during the brazing which is used as a major method for the tube connection. Therefore, development of a copper alloy tube having superior corrosion resistant and brazing properties than the conventional phosphorous deoxidized copper tube is desired as a tube material for the refrigerant tube or the heat exchanger tube.
Further, the fin-tube heat exchanger used for an air-conditioner is generally fabricated using aluminum or aluminum alloy plate fins provided with tube insertion holes and copper tubes. Inside the insertion hole, a tube-type fin collar is provided. Many of said fins are placed in parallel and the copper tube is inserted into said fin collar so as to connect each fin. Then, this tube extended and fixed on the fins. And the heating medium is allowed to flow through the inside of said tube and its heat is transmitted to and radiated from said fins. In this fin-tube heat exchanger, said plate fins are made from aluminum or aluminum alloy due to its thermal conductivity and cost, and, for said tube, the copper tube is widely used from the stand points of its thermal conductivity and corrosion resistant properties. For this copper tube, a pure copper called as phosphorous dioxided copper is mainly used.
However, in these conventional fin-tube heat exchanger, organic materials such as lubricant oil and organic solvents used in the processes of blanking and extending of the tube unavoidably remain on the surface of the tubes, and these organic materials are affected by repeated deposit and evaporation of water during storage of fins and tubes or usage as the heat exchanger. These organic materials are also exposed to the peculiar temperature/humidity and air-exchange environment during usage of the heat exchanger. Under such conditions, these organic materials decomposed to form carboxylic acids which cause the peculiar local corrosion showing the ant-nest type corrosion, resulting in leakage of the tube frequently.
In addition, as aforementioned, although a large amount of lubricant oil has been used during fabrication process of the fin-tube heat exchanger, considering recent environmental problems there is a trend to avoid the degreassing wash by organic solvents and rather to use volatile lubricant oil instead of such organic solvents. Even though the base oil itself is volatile, such lubricant oil still contains some oil additives which may remain on the surface of the copper tube. Therefore, the amount of organic materials remaining on the surface of raw materials is in trend towards increase compared to the case of degreassing wash by organic solvents and the risk for the ant-nest type corrosion is higher than the past.
Under such circumstance, measurements for the ant-nest type corrosion of the fin-tube heat exchanger are attracting the attention of the industry as one of serious problems, and development of a fin-tube heat exchanger having superior corrosion resistant property against the ant-nest type corrosion is desired.